Room temperature, moisture-curable compositions based on .alpha.,.omega.-dihydroxypolydiorganosiloxanes and cross-linkers are known to be useful for the preparation of elastomeric polymers, particularly elastomeric polymers useful in coating, caulking and sealing materials. A desirable property of these compositions is a practically controllable cure rate, i.e. the compositions should cure rapidly enough to become tack-free without undue delay but slowly enough to allow for a reasonable working ("tooling") period.
U.S. Pat. No. 3,280,072 describes the use of mono-aminoalkylalkoxysilanes as cross-linkers in combination with .alpha.,.omega.-dihydroxypolydiorganosiloxanes to produce compositions which upon exposure to moisture cure to form elastomeric polymers. However, the use of certain of these mono-aminoalkylalkoxysilanes, e.g., aminopropyltriethoxysilane, can result in compositions with unacceptably slow cure rates, e.g., requiring seven days or more to vulcanize.
To increase the cure rate of compositions containing .alpha.,.omega.-dihydroxypolydiorganosiloxanes, U.S. Pat. Nos. 3,560,442, 3,621,047 and 3,796,686 propose that the cross-linkers utilized in such compositions should be mono-, bis- or tris-aminoalkyltrialkoxysilanes with a methylene or substituted methylene bridge between the amino and silyl groupings.
In "Kinetics and Mechanisms of Acid- and Base-Catalyzed Hydrolysis of Alkyltrialkoxysilanes in Aqueous Solutions", E. R. Pohl, PROC. 38th. ANN. TECH. CONF., REINFORCED PLASTICS/COMPOSITE INST., S.P.I., SECT 4-B (1983), E. R. Pohl disclosed that substitution of a methyl group for a larger alkyl group as the alkyl moiety of alkyltrialkoxysilanes increased the rate of hydrolysis of the alkoxy groups of alkyltrialkoxysilanes. Since hydrolysis is presumably involved in the curing process of the compositions described in the above-mentioned patents, E. R. Pohl's results are essentially consistent with the results obtained in these patents.
Applicants have discovered, however, that use of the cross-linkers described in U.S. Pat. Nos. 3,560,442, 3,621,047 and 3,796,686 in .alpha.,.omega.-dihydroxypoly-diorganosiloxane compositions can result in compositions that possess an unacceptably fast cure rates, e.g., some of these compositions cure in less than one minute. Such cure rates do not provide for an adequate period for working of the composition.
Accordingly, it is an object of the present invention to provide novel room temperature moisture-curable .alpha.,.omega.-dihydroxypolydiorganosiloxane compositions which possess a practically controllable cure rate, exhibit excellent shelf life stability and, upon curing, produce elastomers which have good adhesion to building materials and which possess good weatherability.
It is another object of the present invention to provide novel poly-(alkoxysilylalkyl)amines useful as cross-linkers in .alpha.,.omega.-dihydroxypolydiorganosiloxane compositions.